Refractory support for ware in a tunnel kiln



Feb. 27, 1951 s. N. JEPPSON REFRACTORY SUPPORT FOR WARE IN A TUNNEL KILN2 Sheets-Sheet 1 Filed 001;. 30, 1948 l/vvs/v TOP Gnoims N. JEPPsoNATToRA/Ey Fig.

Feb. 27, 1951 G. N. JEPPSON 2,543,549

REFRACTORY SUPPORT FOR WARE IN A TUNNEL KILN Filed Oct. 50, 1948 2SheetsSheet 2 /NVENTOR GE ORGE N. JEPPS o N A TTOFIZNEY Patented Feb.27, 1951 REFRACTORY SUPPORT FOR WARE IN A TUNNEL KILN George N. Jeppson,Worcester, Mass, assignor to Norton Company, Worcester, Mass, acorporation of Massachusetts Application October 30, 1948, Serial N 0.57,511

The invention relates to refractory supports for wars in a tunnel kiln.

One object of the invention is to provide a refractory support for warein a tunnel kiln which has a fast heating and cooling .cycle. An-

other object of the invention is to provide a system of batts to supporta .grinding wheel being vitrified in a tunnel kiln of such constructionand arrangement that the batts may be mechanically propelled through thekiln without the use of cars or movable elements other than the battsthemselves and whereby a rapid vitrifying and annealing cycle may beachieved without excessive breakage of the batts due to thermal shock orotherwise. to provide a sliding batt construction especially adapted forthe vitrification of large grinding wheels in a fast heating cycle.Another object of the invention is to provide a support for largearticles to be vitrified in a tunnel kiln having planes of radiantenergy above and below the support.

Other objects will be in part obvious or in part pointed outhereinafter.

The invention accordingly consists in the features of construction,combinations of elements and arrangements of parts, all as will beillustratively described herein and the scope of the application ofwhich will be indicated in the following claims.

In the accompany ng drawings illustrating one of many possibleembodiments of the mechanical features of thi invention, I

Figure l is a plan view showing a plurality of batt elements supportinga single large grinding r wheel to be vitrified and illustrating therods upon wh ch the batts slide.

igure 2 is a cross sectional View taken on the line 2-2 Figure 1.

Figure 3 a cross sectional view taken on the line 33 of Figure 1.

Figure is a longitudinal sectional view through a portion of the heatingor firing zone of a tunnel kiln in wh ch the refractory support of theinvention may be used showing such refractory support in section.

Figure 5 is a cross sectional View of the kiln and sup ort, the sectionbeing taken on the line Ei-5 of Figure l.

Referring first to Figures 1, 2 and 3, in this illustrative embodimentof the invention, a unit which is moved through the kiln comprises fourbatts as which straddle the tunnel and slide on rods 3!, six batts 32which rest upon the batts 3D and extend parallel to the rods 3!, fourend J Another object of the invention is r 7 Claims. (01. 153) bafiles33, two center baffles 34 and a grinding wheel to be vitrified 35.Preferably a layer of quartz sand or the like 35a is placed on top ofthe longitudinally extending batts and the grinding wheel 35 rests uponthis layer. The baffles 33 and and grooves as shown .in Figure 3.

34 may rest upon the longitudinally extending batts 3-2. The purpose ofthe baffles 33 and 34 is to form with the roof and sidewalls of thetunnel and the batts 3E] and 32 a compartment for each grinding wheel asit is being preheated, as it is being fired, and as it is beingannealed. These baflles accordingly have curved edges as shown. A pairof bafiles 33 with a center baffle 36 form a segmental wail followingthe contour of part of the periphery of the grinding wheel 35. By usingthree pieces to form each baflle means ahead of and'behind the grindingwheel, fracturing of such bafile means due to heat shock or thermaldifferential is substantially eliminated.

L kewise the lower support for the grinding wheel 35 consists of fournarrow batts 38 instead of a single batt in order that thermaldifferentials will be less liable to cause fracture. The upper supportfor the grinding wheel 35 consists of six batts 32 for the same reason.Each batt therefore is long in one dimension and relatively narrow. Ihave found that narrow batts will with.- stand a great many cycles ofheat ng and cooling whereas more or less souare batts have a greatertendency to break when subjected to repeated cycles of heating andcooling.

Also by forming the batt sup ort for the wheels in two layers of batts,that is to say a lower layer of batts 3B and an upper layer of batts 32,I provide a support which will withstand many more cycles of heatin andcooling than if the att or batts were in a single layer. Thus it may besaid that the batts are not only narrow, they are also thin. There isanother reason for supporting each wheel 35 by means of a nluralitv ofbatts. A batt in the form of a sin le thick plate or even in the form ofa pair of thin plates superimposed unon each other will warp after anumber ofcyc'les of heating and cool ng. In order to produce grindingwheels with plane sides these grinding wheels should have flat, that isto say planesurfaces to rest upon during vitrification. Another featureof the support for the wheels is the laying of the upper layer of batts32 across insteadof along the lower layer of b it: 39. This helps toproduce a level fiat surface for supporting the wheel 35.

Referring to Figure 2, it will be seen that the fbatts 3!! have a groove36 at one end and a tongue 31 at the other end. These batts extend theent re length of the kiln in a lon line of batts. They arepushed throughthe kiln by a force applied against the end batt at the entrance end ofthe kiln. Consequently each batt 3D is firmly pressed against adjacentbatts and the "tongue and groove junction will hold a broken .batt inplace if the adjacent batts are still whole.

Preferably also the upper batts 32 have tongues As will be noted byreference to Figures 2 and 3, the batts so are thicker than the batts32. Since the batts- 30 are the ones which span the tunnel they are theprimary conveyors of the load.

Figures 4 and 5 illustrate respectively a longitudinal section and across section of a tunnel kiln in which the refractory supports of theinvention can be used. This tunnel kiln has a rectangularparallelepipedal box structure comprising steel side plates 40, steelbottom plates 4i, and steel top plates 42. To the side plates 40 aresecured steel legs 43 and to the bottom plates 4| are secured a numberof centerline legs 46. The bottom plates 4| are braced with angle irons45 and the top of the kiln is strengthened by cross beams 46.

Resting on the bottom plate 4| in the firing zone of the kiln is a mass5!! of refractory bricks forming a generally rectangular paralleleinedal structure the top face 5| of which is the bottom of the tunnel52. This mass 50 stops .iust s ort of the side plates 40 leaving spaceswhich are filled with refractory insulating powder such as porous silica53.

Bricks 54 continue the structure upwardly on either side of the tunnel52 and large bricks 55 continue the structure still further upwardly,the bricks 54 and 55 forming vertical side walls 56 of the tunnel 52 andalso inclined walls 5'! of the tunnel 52.

Secured to the side plates 4!! are lon an le irons 6B which supportchannel irons 6! (Figure 4) arranged in pairs. Each pair of channelirons 6| hel s to support two courses of roof bricks 62. Stating this inanother way, two channel irons 'Sl whose open sides are opposite each oter support between them a course of roof bricks 62 extending clearacross the kiln. These roof bricks 62 in the firing zone are short togive room for the combustion tubes and the burners: roof bri ks 62a arecut away a shown while roof bricks 62b are long to bring down the roofof the tunnel close to t e ware and the baffles 33 and 34. In thereheating zone and in the annealin zone roof bricks 621) are used.

As will clearly be seen. porous silica 53 is locat d in s ces adjacent te side lates u to t e to of the kiln and there is more DOIOlls silica'53 on to oi the roof bricks R2. 620. and 8'").

S p orted bv the bricks 55 are bricks 85 having bor s to receiverefractory tubes 66 on one side of the kiln in which are burners 61. Onthe other side of t e k ln o os te. a b rner 6' the bores in the bricks65 receive refr ctory fine tubes 68 and short refractory tubes 69 inwhich are plu s 1n. I

Simi arl in the m ss of ricks are bri ks 55 havin bores receivin refratorv tu s 5 in w ich ar burners 1. t e bores in the br ck also alte atlv hav n re ractorv flue tubes 68 and s ort r fractorv tub s 69 pluggedw th plu s 10. The t' bes 6 and 68 are conn cted b combustion tub s 15.The arran em nt o urn rs and. time tubes 62 i alt rnate both or zontallyand verticall That is to a on eit er side of a burn r 61 t ere is a fluetube 63 and below a burner 6.1 is a flue tube '68. etc.

Connec ions 16 connect the burners R1 to niping. not shown. which pi nis connected u to sources of gas and air und r pres ure in order tosupnlv t e burn rs 61 with combust n gases. The eases burn mo tlv in theco bustion tubes which. for exam l c n be D1950 o bon ed sili on carbideand \nhlt'th become ery ot. The combustion ea es from t e re ract y fluetubes 68 go into fiues 18 in the bricks 50, 54 and 55 whence they leadto fiues, not shown, to preheat the preheating zone of the kiln. Sincethis invention relates to the refractory supports for the ware, I do notdeem it necessary to describe the entire kiln, and enough of thestructure of the kiln has been described so that the utility of theinvention may be readily apparent.

The rods 3! may be located in grooved elongated refractory members 30which form part of the bottom of the tunnel 52 of the kiln in the firingzone; elsewhere the batts 30 may ride upon rollers, not shown. The batts30 have wide grooves 8| at either end so that they will not slip off therods 3! nor off the rollers, not shown. In the operation 'of this kilnthe operator from time to time places an additional load in front of theentrance end and then causes a ram to push t e new load against the lastprevious load to be introduced and this pushes all the loads ahead of itmoving every load the distance of one section in the kiln and causingone load to move out of the exit end of the tunnel. The assembly ofbatts 30 and with the baffles 33 and 34 and a grinding wheel 35constitutes a unit load. A unit load has a length just equal to onesection of the kiln and one section of the kiln is the distance betweensuccessive legs 43.

For annealing pur oses the batts 39 and 32 may have cut-outs to form ahole 82 in each unit load to allow air to move upwardly through therefractory support in the annealing zone of the kiln.

A solid batt of the overall dimensions of the composite support of theinvention would quickly go to pieces in a tunnel kiln of the typedescribed operating at a top temperature of 1200 C. But the compositestructure of refractory support for wheels to be vitrified enables atunnel kiln of the type illustrated to be successfully operated. It willreadily be seen that this type of tunnel kiln is efficient because theentire supporting means for the ware to be vitrified has a mass notgreatly in excess of the were to be vitrified in contra distinction tothe usual tunnel kiln where the cars and refractory supports have a massmany times that of the ware to be vitrified. Furthermore, the baflies 33and 34 substantially seal off each section of the kiln from every othersection of the kiln and thus optimum preheating, firing and annealingconditions can be achieved. That is to say, at a given time the entirearea of the wheel 35 is subject to the same temperature conditions.There is one exce tion to the foregoing statement, namely thatdeliberately during the annealin the wheels are cool d from the insideto the outside thus to take advantage of the reverse strain annealingdes ribed and claimed in U. S. L tters Patent No. 2.034.721. to mycolleague W. L. Howe dated March 24, 1936. However. so far as the broadfeatures of this invention are concerned, the holes 82 can be omittedand very satisfactory vitrified whees neverthel ss can be produced. Thebafiles 33 and 34 not only protect the wheels 35 from temperaturegradients during all the stages of vitrification, viz. preheating,firing and annealing, but they also protect the batts 30 and 32 fromsuch temperature gradients and. even protect themselves. By providingthese baflles 33 and 34 there is very little difference of temperaturefrom one part to another of any given section of the kiln tunnel 52although there are predetermined differences of temperature be tween anytwo sections.

Batts are customarily made of materials that are matured to a strongcondition at temperakiln furniturehave long been made of refractory fireclays. These give products of satisfactory expansivity characteristicsbut of relatively low strength and low heat conductivity. Siliconcarbide as the main ingredient of batt mixtures gives improved productsbecause in addition to low expansivity they have high strength and highheat conductivity. Likewise, batts composed of mullite which mullite mayhave been essentially originally of the electric furnace fused variety,or may have been developed by the maturing operation to which the battwas subjected in manufacture, have advantages over fire clay batts.Furthermore, refractory batts for very high temperature use may now bemade as sintered or recrystallized products, often substantiallybondless, many of which may be classed as pure oxide refractories. Therefractory supports for ware according to this invention are preferablymade of bonded silicon carbide but so far as the broader features of myinvention are concerned they may be made of other refractory materials.

As an example of a bonded silicon carbide composition for battsaccording to the present invention, I may make a mixture according tothe following formula:

Example Material: Parts by Weight No. 14 to No. 24 grit size siliconcarbide 45 No. 30 to No. 90 grit size silicon carbide No. 100 grit sizeand finer silicon carbide-" 18 Ball clay 12 Dextrine powder 2 Rye flour1 Water -i 4 Total 107 The silicon carbide is the ordinary black gradeand is put into a mixing machine of conventional type and the dextrineis added. After mixing for a minute or two the water is added and mixingis continued for a minute or two more. Then the ball clay and rye flourare screened into the mix together and the mixing is continued for fiveminutes more. This procedure produces a damp granular mixture that issuitable for tamping or pressing. This mixture is then molded in moldsshaped to produce the batts and baffles of the shapes shown, and thenthe green batts and bafiles are fired in a suitable kiln at atemperature substantially higher than the highest temperature which willbe found in the kiln in which they will be used. For example, if thefiring zone of the tunnel kiln herein described is heated to atemperature of 1250 0., the batts and bafiies should be fired to a toptemperature of at least about 140 0 C.

It will thus be seen that there has been provided by this inventionrefractory supports for ware in a tunnel kiln in which the variousobjects hereinabove set forth together with many thoroughly practicaladvantages are successfully achieved. As many possible embodiments may'be made of the above invention and as many changes might be made in theembodiment above set forth, it is to be understood that all matterhereinbefore set forth or shown in the accompanying drawings is to beinterpreted as illustrative and not in a limiting sense.

I claim:

1. A batt assembly comprising a pair of parallel rods, a plurality ofrectangular batts with grooves on the undersides and having dovetailededges in contiguous relation with the dovetails in engagement and withthe grooves on the rods,

and a second plurality of rectangular batts positioned in contiguousrelation transverse to and resting upon the first plurality ofrectangular batts.

2. In a batt assembly as claimed in claim 1, the combination with theparts and features therein specified of a pair of baffles on said secondplurality of batts.

3. An assembly of batts comprising a plurality of rectangular batts withdovetailed edges said batts being located in a plane with the dovetailsin engagement, a second plurality of rectangular batts restingcross-ways upon said. first plurality of rectangular batts, and a pairof bafdes with concavely curved edges resting upon said second pluralityof batts, the planes of the curves of the concavely curved edges of thebaffles being parallel to the planes of both pluralities of batts andthe baffles being located on the second plurality of batts so that thecurved edges face each othzr.

4. In a batt assembly as claimed in claim 3, the combination with theparts and features therein specified of the further feature that each ofsaid baffles consists of a plurality of separate parts.

5. A refractory support for ware in a tunnel kiln comprising two linesof rods said lines being parallel, a plurality of unit loads resting onsaid rods, each load consisting of a plurality of rectangular battshaving grooves on the underside resting upon said rods with the rodsbeing located in the grooves, dovetailed means in each edge of each battwhich runs perpendicular to the lines of rods, all of the batts being indovetailed engagement in a load and from load to load, and in each loadan additional plurality of rectangular batts resting upon the firstdescribed batts said additional batts extending generally in the samedirection as the rods.

6. In a refractory support for ware in a tunnel kiln as claimed in claim5, the combination with the parts and features therein specified of apair of baffles having concavely curved edges in each unit load theconcavely curved edges of the baffles facing each other thus to providean insulated space for a grinding wheel to be vitrified.

7. In a refractory support for ware in a tunnel kiln as claimed in claim6, the combination with the parts and features therein specified of theadditional feature that each baffle is in three parts.

GEORGE N. JEPPSON.

' REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 971,160 Vance -i Sept. 27, 1910979,425 Butler Dec. 27, 1910 1,262,010 Brownlee Apr. 9, 1918 FOREIGNPATENTS Number Country Date 6,139 Great Britain 1914

